Flies

Published: 07/01/2010

As defined by entomologists (scientists who study insects), a fly is any species of insect of the order Diptera. These typically have one pair of true wings, with a set of modified hind wings. Flies are common amongst humans and some can cause the spread of serious diseases. The house fly and mosquito are particularly common amongst humans. Other flies, such as the horse fly, can inflict painful bites. The larva of a fly is commonly called a maggot.
Flies rely heavily on sight for survival. The compound eyes of flies are composed of thousands of individual lenses and are very sensitive to movement. Some flies have very accurate 3D vision. A few, like Ormia ochracea, have very advanced hearing organs.
The diet of flies varies heavily between species. The horse fly eats bits of flesh torn off of its prey, mosquitoes feed on blood and nectar, and the house fly eats a semi-digested liquid created by mixing-enzyme rich saliva with its food.
In addition to being an essential part of the food chain, some species of flies spread pollen, hasten the decomposition of plants, animals, and dung, and, in the case of about 5000 species of Tachina flies, eat other insects.
The fly life cycle is composed of four stages: egg, larva (commonly known as a maggot), pupa, adult. The eggs are laid in decaying flesh, animal dung, manure, or pools of stagnant water - whatever has ample food for the larva.
Some types of maggots found on corpses can be of great use to forensic scientists. By their stage of development, these maggots can be used to give an indication of the time elapsed since death, as well as the place the organism died.
Various maggots cause damage in agricultural crop production, including root maggots in rapeseed and midge maggots in wheat. Some maggots are leaf miners. Maggots are bred commercially, as a popular bait in angling, and a food for carnivourous pets such as reptiles or birds. Due to the increasing popularity of maggots, a maggot vending machine has been installed in the English county town of Northampton.
Through the ages maggots have also been used in medicine in order to clean out necrotic wounds; maggots, applied to an open wound, will quickly eat the dead or necrotic parts of the wound, essentially "cleaning it" of all dead tissue. Once the dead tissue has been properly cleaned the maggots are removed, and the wound can be safely closed.